(a) Technical Field
The present disclosure relates to a method and system for accurately estimating degradation of a high voltage battery within an electric vehicle more accurately, a plug-in hybrid electric vehicle or the like.
(b) Background Art
Generally, a high voltage battery is loaded within an electric vehicle (EV), a plug-in hybrid electric vehicle (PHEV) or the like to store electric energy used as a driving force of the vehicles. When the high voltage battery is used continuously in succession, a degradation phenomenon occurs, thus decreasing the capacity of the battery. When degradation occurs, the accuracy of State Of Charge (SOC) also deteriorates, thereby reducing gas mileage per SOC, deterioration of power for acceleration, or the like.
For this reason, an attempt has been made to determine degradation of a battery by utilizing a battery voltage characteristic and SOC of an EV or PHEV during slow charging. In particular, during slow charging of a high voltage battery loaded within a vehicle, a change in rate of charging capacity with respect to a predetermined voltage change is calculated and compared with known data regarding change rates of charging capacity with respect to a predetermined voltage change during slow charging based on a degradation degree of a high voltage battery of the same specification to detect the corresponding degradation degree.
In a known technique, when detecting a degradation degree using the change of charging capacity in a predetermined voltage region, sensed current values are integrated to measure the change of charging capacity. Since a sensed charging current value is used, a measurement error of a current sensor may be applied, influencing the final degradation degree calculation result. In other words, since a value measured by a sensor is used as a current value for detecting degradation of a high voltage battery in the known technique, an error of the current sensor is applied as an error of the degradation degree. Therefore, when the sensor error increases, the calculated degradation degree also has an increased error.
During the slow charging of a high voltage battery, a slow charger receives power from an external power source to charge the vehicle battery. Therefore, the charging current may vary according to specifications of the input power (e.g., output specifications). Therefore, in the known technique, degradation may be detected in the power source having predetermined specifications.
The above information disclosed in this section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.